I have been granted U.S. Pat. No. 4,938,457 for apparatus, a suspended centrifuge, for treating aluminous metal skim material. The apparatus is used in the skim reclamation method for which I was granted U.S. Pat. No. 4,137,073 which method recovers aluminum metal and produces a residue which is especially easy to process for additional value recovery. Nothing is wasted; energy consumption is low.
As pointed out in my U.S. Pat. No. 4,938,457 there are important advantages to using a suspended centrifuge to extract liquid. I have found these advantages especially important when initially unbalanced loads of greater than about 200-kilograms are to be centrifuged. The apparatus, in a commercial form to treat aluminum skim, will spin loads of about 500-kilograms (about 1,000-pounds) or more of hot aluminous alloy skim at temperatures above about 650.degree. C. (about 1,200.degree. F.). To retain the benefits of a suspended centrifuge I have found that at least a majority of the rotating mass must be suspended and no more than about 200-kilograms should be carried on a fixed base regardless of the mass suspended.
There is a shortcoming that can occur in the operation of the suspended centrifuge apparatus of my U.S. Pat. No. 4,938,457. It is possible, during rotation, for the suspended centrifuge vessel to lose its initial, static, vertical axis such that the vessel's central axis tends to pivot towards the horizontal about the suspension linkage interconnecting point. That is, the suspended vessel can precess or gyrate, describing a conical surface, around an initial vertical axis. Gyration, once begun, shows an apparent tendency to increase with rotational speed and perhaps with time. Loss of a vertical axis by more than about 5-degrees, measured from the linkage interconnecting point, results in an operationally inferior system both with respect to control of liquid discharge trajectory and to possible or real damaging contact between the rotating vessel and stationary objects, such as collection means, located adjacent to the gyrating vessel.
Because of the nature of gyration, a physical restraint is necessary. The force required to maintain the vertical axis of vessel rotation seems inversely related to the length from suspension linkage interconnecting point to base of bowl (a distance that can be considered analogous to a lever arm distance) and also seems related to the degree the vessel's central axis is out of true vertical. I found it best to locate the restraint as far from the pivot of gyration (the linkage interconnecting point) as is practical and to limit the freedom to gyrate to a minimum consistent with maintaining an effectively suspended centrifuge, that is, keeping all or most of the weight suspended.